Microminiaturization of a circuit pattern of a semiconductor integrated circuit is advanced to attain improvement of performance. According to the microminiaturization of the circuit pattern, more strict accuracy is required for measurement of the circuit pattern. In a semiconductor process in the past, relatively rough dimensions such as width and height are targets of management concerning a unit structure included in a periodical structure. On the other hand, according to the advance of the microminiaturization of the circuit pattern, there is also a need for strictly measuring detailed dimensions of a shape such as roundness of an upper part of the unit structure called top rounding and roundness of a lower part of the unit structure called bottom rounding.
As technologies for precisely observing a sectional shape of a structure, for example, a scanning electron microscope (sectional SEM), a transmission electron microscope (TEM), an atomic force microscope (AFM), scatterometry, and critical dimension small angle X-ray scattering (CD-SAXS) are known. Among the technologies, the CD-SAXS for measuring a surface shape using X-ray small angle scattering is suitable for measurement of a micro circuit pattern from a viewpoint that satisfactory sensitivity with respect to a micro shape can be obtained in a non-destructive non-contact manner.
For example, Japanese Patent Application Laid-Open No. 2003-254920 proposes a technology of an X-ray analysis method and an X-ray analysis system for evaluating and correcting reliability of spectra of X rays. In such a technology, the reliability of the spectra is evaluated by dividing an integration time for accumulating X-ray intensity and monitoring a temporal change of peak intensity in the spectrum.
In the CD-SAXS, in general, an X-ray vessel is used as a light source. Usually, the X-ray vessel needs to irradiate light for a long integration time to obtain light intensity of a degree enough for measuring an intensity distribution of light scattered by a periodical structure. Therefore, a longer measurement time is required as higher accuracy is required for measurement. This causes deterioration in throughput in total of substrate measurement.